First, you're using the wrong $data variable. Second, as Corion points out, you need to protect with if.

my $data = 'blabla;tag1=12345;blabla;tag2=99999';

my $tag1;
my $tag2;

$data =~ /tag1=(\d+)/;
$tag1 = $1 if $1;

$data =~ /tag2=(\d+)/;
$tag2 = $1 if $1;

#
# or
#

# the '?' in the below regex means it'll grab the closest
# tag2, and ignore any beyond it

($tag1, $tag2)
  = $data =~ /tag1=(\d+).*?tag2=(\d+)/ if $1 && $2;

print "$tag1, $tag2";
[download]

Update: I could have sworn you were using $2 in the second match. If that was the case and you edited your post, I want to point out that when doing independent matches, the second run to get a match will re-use $1. To use $2, you need both capture groups within a single regex.

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